1. Field of the Invention
The present invention relates to a fastening screw, and more particularly to a fastening screw with a lacking function for preventing loosening thereof after being tightened.
2. Description of the Prior Art
A fastening screw is used in a variety of..industrial field since it can be used for connecting a plurality of members with ease. However, in this kind of screw, generally, the torque for loosening the screw is small and the screw is susceptible to inverse rotation or loosening due to vibration after being tightened.
To solve the problem, a spring washer, double nuts or the like are applied when bolts and nuts are used. Further, when the tapping screw is adopted, a locking washer or bonding agent is preferably adapted.
The present inventor has proposed a tapping screw suitable for synthetic resin in Japanese Patent Application No. Heisei 2-246203, and another fastening screw with locking function which is preferably used for relatively soft metal such as an aluminum die casting in Japanese Patent Application No. Heisei 2-411007.
However, the above fastening screws are not suitable for a thin plate such as a thin steel plate, and no fastening screw is proposed to effectively prevent the loosening thereof when used for the thin plate.